Anyone like myself who finds themselves in the realm where the airsoft and firearms communities overlap are familiar with the debate over the viability of airsoft guns for firearms training. It goes back a long time. I have used gas blowback pistols for training many years. The cost of operating an airsoft gun, although not inexpensive, is like night and day when compared to a real firearm. For that reason alone I am a proponent of using airsoft for training. It comes with limitations but it is one more tool for the tool box.
And, more recently airsoft has been gaining momentum in the firearm community as a viable training tool, especially as ammo prices have soared. Travis Haley of Haley Strategic Partners, well established in the firearm community, has endorsed airsoft guns as a means for training in a recent video
and does an excellent job of explaining the advantages.
I remember getting the occasional law enforcement orders years back for gas blowback pistols because functionally they were quite similar to their real firearm counterparts but the demand was never that great for rifles and I feel one of the primary reasons was the dominance of AEGs on the market. At the time although useable for force on force training they had several shortcomings such as being dimensionally different then real firearms since they need to house a gearbox, motor, and battery. I will not detail all the shortcomings as that would take an inordinate amount of your time and mine.
Developments like the Systema PTW and others fixed some of the problems. For example, the Systema PTW used a new motor and gearbox design that aside from being more efficient enabled the PTW to have a proportionally correct size pistol grip and receiver. Also, the Systema PTW design had a functional "bolt release." I emphasize bolt release because that is what it was meant to simulate, the release of the bolt carrier group to chamber the first round after inserting a new magazine. But in reality the Systema PTW did not have a bolt at all.
That was the shortcoming of the PTW and similar systems; the lack of a bolt carrier group. As a result the charging handle and forward assist did not function. Since the release of the PTW there have been blowback AEGs but that normally consists of a thin metal plate "recoiling" back. Aside from that they are not functionally different from conventional AEGs.
Enter the gas blowback rifle. Over about the last 2 years the airsoft market has seen the emergence of gas blowback rifles. Although gas rifles have been around many years they have been outshined by AEGs but models like the King Arms gas blowback M4 and others have addressed the shortcomings of AEGs, at least in the training sense. The design of such gas blowback rifles bring airsoft guns to a new level as training tools. Like the Systema PTW they are dimensionally similar if not that same as their real firearm counterparts.
The difference comes down to the internal operation. There is not an electrical switch. When you pull the trigger a hammer is released, a bolt carrier group recoils/blowsback; into a buffer tube that has a buffer and spring. As a result the trigger feel, fieldstrip/breakdown, controls, felt recoil are all more realistic. Every sensation and operation is enhanced. The near future release of KWA's gas blowback M4, the LM4, gives me further hope for the future of the gas blowback airsoft rifle as a training tool. KWA promises it will out perform and provide greater efficiency then current platforms.
The only significant shortcomings from my perspective remaining with the gas blowback rifles is they function less efficiently in cold and no marking ability. I discount the decreased accuracy as compared to a real firearm out of hand as my primary concern as a training tool is for force on force scenarios and weapons manipulation practice. In regards to the remaining shortcomings we are light years ahead of where we were a couple years ago. I was there, I remember. The desire is always to have the perfect system but in this world nothing is perfect so for the time being such shortcomings can be worked around and should not deprive us of a viable training tool.